What you can do before applying for AdSense is to make sure you have the most important and basic steps are done for getting approved.
They would be:
1. Quality Articles ( quality = human readable, seo-friendly article, e.g headings,etc & a little unique to google search engine) , around 10-20 with 350-500+ words, already published and they are indexing on Google
2. Template, it should be simple and user friendly.
3. Improving Site speed, you can check google page speed insights for it, it can help boost indexing ( indexing helps a lot on getting approved ).
if you got these steps already done, then 60 or 70% i can assure you the site is ready for getting approved.
& yes you can re apply as many times until you get approved.
Sometimes, adsense disapproves for no reason even though your site is all ready, in this case keep reapplying you will get approved on 3rd or 4th try.